'Nào bièniu' literally combines 'nào' (to make a fuss, stir up), 'biè' (to be contrary, stubborn), and 'niu' (to twist, turn away). Together, it describes the emotional behavior of sulking — withdrawing affection or cooperation in a petty, childish way after a minor disagreement or perceived slight. It’s not about serious conflict but rather passive resistance: refusing to speak, giving cold shoulders, or acting overly sensitive without openly expressing the real grievance.

This phrase is commonly used in close personal relationships — between spouses, romantic partners, parents and children, or good friends — where emotional safety allows for such expressive, low-stakes tension. It carries a slightly affectionate or teasing connotation when used by outsiders ('They’re闹别扭 again'), but can sound critical if said by someone directly affected. The tone is informal and conversational; you won’t find it in formal writing or official speech.